It can be presumed that you are preparing for Civil services Preliminary Examination and you are aware of the CSE pattern. My answer would confine to your Preliminary Examination. The Civil Services Preliminary exam would consist of two papers 200 marks each (General Studies Paper I and General Studies Paper II) and will be of objective type and MCQs to get qualified for the main examination.
The topics covered in the examination include Current events of national and international importance, History of India and Indian National Movement, Indian and World Geography, Indian Polity and Governance, Economics, Environmental, and General Science.
As such, you need to be through with the current events in India and abroad. Follow the Newspapers and news reports regularly. Collect all the NCERT books related to Social studies, geography, and Economics from Class VI to X which will help you a lot. Competition Success Review (CSR) is lending a helping hand to the Civil services aspirants for more than five decades and subscribe for it. GK Today, Indian and Foreign Review, Manorama Year Book, Yojana and many other competitive magazines like Competition Adviser would help you a lot. For paper II, the areas covered are- Comprehension, communication skills, Logical reasoning, and analytical ability, Decision-making and problem-solving, General mental ability and Data Interpretation. If you go through any CAT examination preparation guide, you can pick the elements of learning. Coaching in a reputed institute would always be a valuable addition to your preparation.